Ultra High Frequency Radio Frequency Identification System Research Articles

Performance of a UHF RFID Detection System to Assess Activity Levels and Lying Behaviour in Fattening Bulls

Animal welfare strongly influences the health and performance of cattle and is an important factor for consumer acceptance. One parameter for the quantification of health status is the lying duration, which can be deployed for the early detection of possible production-related illnesses. Usually, 3D-accelerometers are the tool to detect lying duration in cattle, but the handling of bulls sometimes has special requirements because frequent manipulation in daily farming routines is often not possible. An ultrahigh-frequency (UHF) radio-frequency identification (RFID) system was installed in a beef cattle barn in Germany to measure the activity and lying time of bulls. Such UHF RFID systems are typically used for estrus detection in dairy cows via activity level, but can also be considered, for instance, as an early detection for lameness or other diseases. The aim of the study was to determine whether the estimations of activity level and lying duration can also be traced in husbandry systems for fattening bulls. Two groups of bulls (Uckermärker cattle, n = 10 and n = 13) of the same age were equipped with passive UHF RFID ear transponders. Three cameras were installed to proof the system and to observe the behaviour of the animals (standing, lying, and moving). Furthermore, accelerometers were attached to the hind legs of the bulls to validate their activity and lying durations measured by the RFID system in the recorded area. Over a period of 20 days, position (UHF RFID) and accelerometer data were recorded. Videos were recorded over a period of five days. The UHF RFID system showed an overall specificity of 95.9%, a sensitivity of 97.05%, and an accuracy of 98.45%. However, the comparison of the RFID and accelerometer data revealed residuals (ԑ) of median lying time (in minutes per day) for each group of ԑGroup1 = 51.78 min/d (p < 0.001), ԑGroup2 = −120.63 min/d (p < 0.001), and ԑGroup1+2 = −34.43 min/d (p < 0.001). In conclusion, UHF RFID systems can provide reliable activity and lying durations in 60 min intervals, but accelerometer data are more accurate.

Efficient Modeling of On-Body Passive UHF RFID Systems in the Radiative Near-Field

A novel method is presented to accurately determine the operational range of an on-body, passive ultrahigh-frequency (UHF) radio frequency identification (RFID) system operating in the radiative near field, based on its far-field radiation patterns. To this end, an efficient algorithm based on 3-D multipole expansion of the electromagnetic fields is formulated. By combining the new operator with the simulated or measured stand-alone far-field radiation patterns of the on-body RFID system, a comprehensive and accurate range determination is obtained. Compared with commercial software tools and measurements, we prove the accuracy and improved speed of the novel technique.

A Data Augmentation-Based Method for Robust Device-Free Localization in Changing Environments of Passive Radio Frequency Identification System

Device-free localization (DFL) is playing a critical role in many applications which do not require any device attached to the target. Because of environmental changes, the fingerprint database established in the original environments is unable to remain effective when used in the changing environments. Looking at dropout as a prior-knowledge-free data augmentation operation, we propose a convolutional denoising autoencoder (DAE)-based DFL architecture AugRF. Our method combines the merits of the convolutional neural network and the DAE in which convolutional operation is beneficial to feature extraction and dropout operation is equivalent to generating augmented versions of the training data. It is noted that our method can improve the localization performance in changed environments without resampling and retraining processes. Simulations and real-world experiments verify the superiority of the proposed architecture. Our localization system can be implemented with a commercial ultrahigh-frequency radio frequency identification system. When the signal-to-noise ratio of the fingerprint data drops significantly due to environmental changes, AugRF contributes to improving localization accuracy. In addition, the time cost for one positioning meets the requirement of real-time indoor localization.

Setup, Test and Validation of a UHF RFID System for Monitoring Feeding Behaviour of Dairy Cows.

Feeding behaviour can be used as an important indicator to support animal management. However, using feeding behaviour as a tool for dairy cow management an automatic sensor system is needed. Hence, the objective of this study was to setup, test and validate a ultra-high frequency (UHF) radio-frequency identification (RFID) system for measuring time dairy cows spent at the feed fence using two types of passive UHF ear tags. In a first experiment, the reading area of the system was evaluated in two antenna positions. Subsequently, the UHF RFID system was validated with video observations and compared to the measurements of chewing time of a noseband pressure sensor and of the time spent at the feed fence registered by a sensor system with real-time localisation. Differences in the reading area were detected between the two antenna positions and types of ear tag. The antenna position leading to less false positive registrations was chosen for the experiment with cows. The validation with video data showed a high average sensitivity (93.7 ± 5.6%, mean ± standard deviation), specificity (97.8 ± 1.1%), precision (93.8 ± 2.3%) and accuracy (96.9 ± 0.9%) of the UHF RFID system for measuring the time spent at the feed fence. The comparison with the noseband pressure sensor and the real-time localisation resulted in high correlations with a correlation coefficient of r = 0.95 and r = 0.93, respectively. However, substantial absolute differences between the three systems pointed out differences between direct and indirect measures of feeding behaviour in general and between the different sensors in particular. Thus, detailed considerations are necessary before interpreting automatically measured feeding data generally.

A Support Vector Machine Classification-Based Signal Detection Method in Ultrahigh-Frequency Radio Frequency Identification Systems

Noise and distortion in real signals have posed challenges in signal detection in ultrahigh-frequency (UHF) radio frequency identification (RFID) systems, with the exception of large frequency deviation. In this article, signal detection in a UHF RFID system was treated as a time-series classification problem. A support vector machine-based detector was proposed for real-time signal detection to optimize the system performance. The improved system was able to achieve frame synchronization detection and time-series data detection with a frequency deviation of ± 22%. With the analysis of the frame format, the frame synchronization was based on the sequence detection with the most likely selection, and the data detection was performed using a symbol-by-symbol method with two-step adjustments in order to reduce time and hardware costs. The algorithm was mainly trained offline using the experimental data, and then efficiently implemented in a UHF RFID system based on a software-defined radio platform. The system was validated on real-time signals of commercial tags. The experimental results showed that the learned detector had displayed improvements in detection accuracy and stability when compared to the existing method based on a correlation algorithm.

Compact broadband circularly polarized UHF RFID tag antenna for metallic mounting

ABSTRACT We report a broadband ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna of compact size mounted on a metallic object in a near field communication (NFC) RFID system. One half of the square radiation patch has a semi-annular strip feedline embedded inside a semicircle-shaped slot to improve the antenna bandwidth and gain, and the other half of the radiation patch has an L-shaped slot and a shorting pin to increase the circular polarization (CP) bandwidth and reduce the antenna size. The resonant input impedance of the tag antenna can be tuned easily by varying the length of the semi-annular feedline, and the gap between the feedline and the etched semicircular slot. The proposed tag antenna has a wide measured impedance bandwidth (−10-dB |Γ|) covering the whole operating frequency range of 181 MHz (from 790 to 971 MHz) for a UHF RFID system. The measured 3-dB axis ratio (AR) bandwidth is 43 MHz (from 895 to 938 MHz), which is much larger than those of the CP tag antennas reported in the literature for metallic objects. Further experiment has shown that the proposed tag antenna can provide a stable reading range when mounted on metal plates of various sizes.

A Group-Based Binary Splitting Algorithm for UHF RFID Anti-Collision Systems

Identification efficiency is a key performance metrics to evaluate the ultra high frequency (UHF) based radio frequency identification (RFID) systems. In order to solve the tag collision problem and improve the identification rate in large scale networks, we propose a collision arbitration strategy termed as group-based binary splitting algorithm (GBSA), which is an integration of an efficient tag cardinality estimation method, an optimal grouping strategy and a modified binary splitting. In GBSA, tags are properly divided into multiple subsets according to the tag cardinality estimation and the optimal grouping strategy. In case that multiple tags fall into a same time slot and form a subset, the modified binary splitting strategy will be applied while the rest tags are waiting in the queue and will be identified in the following slots. To evaluate its performance, we first derive the closed-form expression of system throughput for GBSA. Through the theoretical analysis, the optimal grouping factor is further determined. Extensive simulation results supplemented by prototyping tests indicate that the system throughput of our proposed algorithm can reach as much as 0.4835, outperforming the existing anti-collision algorithms for UHF RFID systems.

Recovery of collided RFID tags with frequency drift on physical layer

In a passive ultra-high frequency ( UHF ) radio frequency identification ( RFID ) system, the recovery of collided tag signals on a physical layer can enhance identification efficiency. However, frequency drift is very common in UHF RFID systems, and will have an influence on the recovery on the physical layer. To address the problem of recovery with the frequency drift, this paper adopts a radial basis function ( RBF ) network to separate the collision signals, and decode the signals via FM0 to recovery collided RFID tags. Numerical results show that the method in this paper has better performance of symbol error rate ( SER ) and separation efficiency compared to conventional methods when frequency drift occurs.

A Circularly Polarized Antenna Array with Gain Enhancement for Long-Range UHF RFID Systems

A 2 × 2 circularly polarized (CP) sequential rotation microstrip patch antenna array with high gain for long-range ultra-high frequency (UHF) radio frequency identification (RFID) communication is proposed in this paper. In order to meet the operational frequency band requirement of 840–960 MHz and, at the same time, achieve enhanced broadside gain, a two-level sequential rotation structure is developed. Series power divider is used as the basic element of the feed network that is implemented with the substrate-integrated coaxial line technology for minimizing radiation losses. The manufactured prototype exhibits a peak gain of 12.5 dBic at 900 MHz and an axial ratio (AR) bandwidth (AR ≤ 3 dB) of 18.2% from 828 to 994 MHz. In comparison with the state-of-the-art, the proposed antenna shows an excellent gain/size trade-off.

An ultra-high frequency radio frequency identification system for studying individual feeding and drinking behaviors of group-housed broilers

Radio frequency identification (RFID) technology offers a real-time solution to monitor behavioral responses of individual animals to various stimuli, which provides crucial implications on farm management and animal well-being. The objectives of this study were to (1) develop and describe an ultra-high frequency radio frequency identification (UHF-RFID) system for continuously monitoring feeding and drinking behaviors of individual broilers in group settings; and (2) validate the performance of the UHF-RFID system against video analysis in determining the instantaneous bird number (IBN) and time spent (TS) at feeder and drinker. The UHF-RFID system consisted of cable-tie tags, antennas, a reader and a data acquisition (DAQ) system. The antennas generated electromagnetic fields where tags were detected and registered by the DAQ system. Electromagnetic fields of the antennas were modified to cover areas of concern (i.e. tube feeders and nipple drinkers) through a series of system evaluations and customizations including tag sensitivity test, power adjustment, radio wave shielding, and assessment of interference by add-ons (e.g. plastic wraps for protecting antennas and an empty carton box for zoning out broilers) and feed/feeder. System validation was performed in two experimental rooms, each with 60 tagged broilers. The results showed that the max reading distances of tags with an identical manufacturer’s specification were markedly different, indicating large variations in sensitivity among the tags. Desired electromagnetic fields could be achieved by adjusting the power supplied to antennas and by partially shielding antennas with customized stainless steel sheets. The protection materials and fully loaded feeder had little effect on electromagnetic fields of the antennas. The accuracies of the UHF-RFID system for determining IBN and TS were, respectively, 92.5±4.2% and 99.0±1.2% by the feeder antennas and 94.7±4.2% and 93.7±6.9% by the drinker antennas. It is concluded that the UHF-RIFD system can accurately detect and record feeding and drinking behaviors of individual broilers in group settings and thus is a useful tool for investigating impacts of resource allocations and management practices on these behaviors.

The influence of food composition and tag orientation on UHF RF IDentification

Ultra-high frequency (UHF) radio frequency (RF) labelling is considered to be one of the most promising techniques for automatic identification through all food supply chain phases. However, the efficacy of RF IDentification (RFID) systems has proven critical for some food products.In this paper the role of the composition and the temperature of the food product and of the mutual label-reader orientation on identification performances is investigated. For this purpose, basic food constituents, prepared as solutions (salts, sugars, organic acids and ethanol) at different concentrations and temperatures, were considered and then the identification results were compared to those obtained from whole food products.The results show how the reading performances of UHF RFID systems are influenced by the considered parameters. The reading ranges for the identification of critical food products by UHF RFID systems can be estimated and then improved by considering the composition of the food product directly from the design phase.

Long read range Class‐3 UHF RFID system based on harmonic backscattering

A high sensitivity Class-3 ultra high-frequency (UHF) radio-frequency identification (RFID) system based on harmonic backscattering to achieve a long read-range is presented. Harmonic backscattering is a promising solution to solve the carrier leakage issue of UHF RFID reader to improve the sensitivity. In the proposed RFID system based on harmonic backscattering, the RFID reader transmits data with the fundamental frequency carrier and receives data with its second harmonic carrier, and the RFID tag employs a rectifier to generate both DC power and the second harmonic carrier for backscattering without impedance mismatch. The first harmonic Class-3 UHF RFID system based on National Instruments software defined radio platform is proposed and implemented. The proposed semi-passive harmonic RFID tag has dBm sensitivity. Test results show that the harmonic RFID system has a dBm sensitivity with the harmonic RFID tag whose signal-to-blocker ratio is dB at 20 m communication distance.

UHF RFID system for wirelessly detection of corrosion based on resonance frequency shift in forward interrogation power

A radio frequency identification (RFID) based system is developed in this paper as a novel passive wireless sensor to detect corrosion for structural health monitoring (SHM) of metallic surface through simulation, design, fabrication and experiment. Firstly, a 2D label-type antenna in a new configuration – circular three arm (CTA) element – is designed as an ultrahigh frequency (UHF) RFID sensor tag working on surface of steel samples. To improve gain and power transmission coefficient, a parasitic element has been added into the centre of CTA. The CTA antenna attached with the parasitic element – so called (CTAP) sensor – has a quality factor notably higher than similar metal mountable UHF RFID antennas that has been resulted to revelation of resonance frequency in measured forward interrogation power. A demonstration and validation system are introduced then to detect corrosion based on the shift of revealed resonance frequency in the forward interrogation power to activate the CTAP tag when placed on surface of corroded and non-corroded steel samples. Results show that the presented system could communicate with sensor tag to detect corrosion up to 2 m of read monitoring range at the UHF RFID standard bandwidth with a sensitivity around of 13 MHz.

Printed UHF RFID Reader Antennas for Potential Retail Applications

Automation of retail industry is calling for the low cost solution due to its sheer size and varied needs. Printed electronics offers a great potential in addressing the needs in point-of-sales, inventory management and self-service, in particular the radio frequency identification (RFID) systems consisting of the printed components. Screen printed Ultra high frequency (UHF) RFID reader antennas have been investigated in this work for their application potentials in retails for achieving easy-implementation and low cost. The results obtained clearly demonstrated that the screen printed UHF RFID reader antennas are closely matching the performance of their circularly polarized patch antenna counterparts fabricated using the conventional chemical etching method in most critical specifications. The screen printed antennas have been explored for the monitoring of items on metal shelves targeting potential inventory management and point-of-sales applications. It has been found that all tagged items can be identified using a home developed UHF RFID system consisting of the printed antennas. The findings pave the way for the use of low cost printed antennas in the potential retail automation applications.

Collision Detection and Signal Recovery for UHF RFID Systems

In this paper, we present a novel high-throughput anti-collision algorithm for passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) systems. Our algorithm utilizes signal recovery techniques of collided tag signals to both recover tag communications and obtain an accurate count of all tags in the field. Passive UHF RFID systems are used for long-range passive communications for applications including supply chain management and electronic tolling. Anti-collision algorithms are used to ensure successful RFID tag communications due to the likelihood of multiple tags being in the field and attempting to communicate simultaneously. The limited on-tag functionality necessitates the use of simple anti-collision algorithms such as a dynamic frame slotted Aloha (DFSA) algorithm. With our novel collision detection and signal recovery anti-collision algorithm, the RFID reader can retrieve multiple valid communications from each collided slot in a DFSA-based anti-collision protocol, while our algorithm allocates an optimal number of slots resulting in more collided but recoverable slots and fewer empty slots. Our algorithm achieves a nearly 100% throughput improvement with an expected throughput of 0.85 compared with an expected throughput of 0.426 for a standard DFSA algorithm. The reader receiver with the proposed algorithm is implemented in a field-programmable gate array and the whole reader system is verified using the communication tests with commercial tags. According to the synthesized results in an SMIC 0.13- $\mu \text{m}$ CMOS technology, the collision detection and signal recovery module consumes about 135k GE. Note to Practitioners —Signal recovery methods are capable of extracting information from collided signals. In this paper, we introduce and analyze a signal recovery method based on the voltage histogram of the received signal. Both the original signals and the number of collided signals are recovered. The information of tags is used by our novel algorithm to increase the system throughput in DFSA-based anti-collision algorithms. The recovered signals allow our algorithm to directly obtain the tag identifier. By determining the number of collided signals, our algorithm is able to calculate an accurate estimate of the total number of tags in the reader’s field. With signal recovery and an accurate tag count, our algorithm is able to reduce the total number of slots needed to identify all tags, thereby increasing the throughput. We present a novel frame length optimization method that increases throughout by shrinking the number of slots, thereby intentionally causing collisions and reducing the total number of empty slots. In addition, we present a hardware implementation of our novel method that is suitable for integration into RFID readers. When the signal strengths of the tags in collision in the in-phase or quadrature path are not close to each other, the performance of our method is much better than that of the traditional method in which the collision signal is treated as ineffective and ignored.

Ultrahigh Radio Frequency (820-960 MHz) Identification System Affects Antioxidant Barrier in Red Blood Cell Concentrates

Background and objectives: Radio frequency identification (RFID) tags have advantages over bar codes in blood management system. Ultra-high frequency (UHF) RFID technology (820-960 MHz) in many ways has more advantages than high frequency (HF) RFID (13.56 MHz). The aim of our study was the evaluation of the effects of UHF RFID in comparison to HF RFID radiation on quality markers of RBC and on the oxidoreductive balance in RBC stored in containers labelled with RFID tags. Materials and methods: Ten RBC units were split into three components, one control unit-marked with bar code and two test units labeled with RFID tags - one operating on UHF and the second on HF radio waves. All units were stored at 2-6°C for 35 days. The test groups were exposed to radio waves continuously during storage. The quality parameters as well as concentration of malondialdehyde (MDA), and activities of superoxide dismutase, glutathione peroxidase and glutathione reductase were measured. Results: The degree of hemolysis and the concentration of K+ were statistically significant higher on 35th day of storage in RBC labelled with UHF RFID tags compare to control and HF RFID groups. On the 35th day of storage the concentration of MDA was statistically significant higher and the activities of oxidoreductive enzymes were statistically significant lower in the UHF group compare to control and HF groups. Conclusion: UHF RFID tags affect oxidoreductive balance in RBC and may lead to eryptosis. The approval of UHF RFID system for blood components needs further studies.

Influence of Temperature on the Dynamic Reading Performance of UHF RFID System: Theory and Experimentation

Abstract The radio frequency identification (RFID) system is vulnerable to a variety of factors (metal, liquid, temperature, and so on) in the practical application. In this paper, the reading distance of tags, as the evaluation criteria for the reading performance of the RFID system, is focused on to study the influence of environmental temperature on the dynamical performance of an ultra-high frequency (UHF) RFID system. An experimentation system, including temperature control system and detection platform, is devised to control temperature and measure the reading distance of the RFID tag. According to the experimental data of the tag's reading distance at different temperature, a fitting model between temperature and tag's reading distance is established. Experimental results show that the tag's reading distance decreases with the increase of temperature. Finally, the corresponding temperature compensation mechanism is deduced to get the reading distance under the same reference temperature. This paper provides an effective method for selection and evaluation of UHF RFID tags at different temperature.

IoT Localization for Bistatic Passive UHF RFID Systems With 3-D Radiation Pattern

Passive radio-frequency identification (RFID) systems carry critical importance for Internet of Things (IoT) applications due to their energy harvesting capabilities. RFIDbased position estimation, in particular, is expected to facilitate a wide array of location-based services for IoT applications with low-power requirements. In this paper, considering monostatic and bistatic configurations and 3-D antenna radiation pattern, we investigate the accuracy of received signal strength-based wireless localization using passive ultra high frequency RFID systems. The Cramer-Rao lower bound (CRLB) for the localization accuracy is derived, and is compared with the accuracy of maximum likelihood estimators for various RFID antenna configurations. Numerical results show that due to RFID tag/antenna sensitivity, and the directional antenna pattern, the localization accuracy can degrade at blind locations that remain outside of the RFID reader antennas' main beam patterns. In such cases optimizing elevation angle of antennas are shown to improve localization coverage, while using bistatic configuration improves localization accuracy significantly.

Wheat gluten, a bio-polymer to monitor carbon dioxide in food packaging: Electric and dielectric characterization

The use of wheat gluten as sensing material to detect carbon dioxide is a promising approach. The dielectric properties of wheat gluten are modified in contact with carbon dioxide gas at high relative humidity (90%) and at a temperature of 25°C due to a structural change in the sensing material, where amino groups act as receptors to carbon dioxide molecules. In the present study, the effects of carbon dioxide on the electrical and dielectric properties of wheat gluten at 20% and 90% of relative humidity (usually found in food packaging) are determined and discussed. At 90% of relative humidity, a linear increase of the dielectric permittivity and dielectric loss was observed with a significant hysteresis which increased with the number of carbon dioxide treatment cycles. One of the significant results is the increase in the dielectric permittivity from 7.01±0.07 to 12.02±0.03 with a sensitivity of 31.38±0.06fF/%CO2 measured at 868MHz. The developed sensor is sought to be integrated in the design of UHF-RFID (ultra-high frequency − radio frequency identification) systems working at 868MHz.

Range Estimation and Performance Limits for UHF-RFID Backscatter Channels

The accuracy of time-of-flight-based ranging over ultra-high frequency (UHF) radio frequency identification (RFID) backscatter channels is fundamentally limited by the available bandwidth and highly dependent on the channel characteristics. Comprehensive wideband channel measurements are presented and analyzed with respect to parameters which influence the potential ranging performance. The Cramer Rao lower bound on time-of-flight-based ranging is evaluated and we study the influence of dense multipath on the bound. Based on a line-of-sight (LOS) plus dense multipath (DM) radio channel model, a multiple-input multiple-output (MIMO) ranging algorithm is developed, capable of iteratively estimating the LOS parameters and the statistics of the DM. The accuracy of the developed algorithm is compared to the performance bound. The results highlight the tradeoff between a higher bandwidth and spatial diversity for UHF RFID systems with respect to time-of-flight-based ranging. In a $\boldsymbol {2\times 2}$ MIMO setup, an accuracy of about 0.5m is achieved at a bandwidth of 50 MHz.